How to Read a Fish Finder

How to Read a Fish Finder

The technology used in making fish finders is quite advanced which makes it accurate and effective in identifying topography under the water and locating ideal fish grounds. This includes underwater structures and drop offs such as wrecks, sunken trees and mounds. Plus, it helps identify individual fish and a school of fish with precision.

However, most beginners find trouble reading what’s displayed on the LCD screen of the fish finder. You are at the right place if you can relate. This article will let you in on how to read a fish finder correctly and interpret different results to help improve your chances of catching more fish.

Basics of a Fish Finder

By now, you already know that most fish finders usually use sonar technology to give you detailed information about the structure underneath the kayak or boat. Advanced fish finder technology is typically based on receiving and sending sonar signals.

The fish finder’s transducer sends the sonar signals, also known as sonar cone right into the water. The sonar signals cast back upwards when they hit an object then the receiver interprets the signal that just returned, displaying them on the screen as shapes. The sonar beam in most fish finders is usually relatively narrow meaning the user can see anything underneath the vessel easily. You’ll be in a position to spot better fishing opportunities once you master the art of applying it to achieve maximum effect.

However, the sonar technology only works in the water. It can’t work on the surface or air. You can tell the temperature and depth of the water once you learn how to read the screen of the fish finder correctly. What’s more, it also allows you to estimate the size of the fish.

How to Read the Screen of a Fish Finder

Fish Dots vs Fish Arches

Fish finders that use 2D sonar that include the CHIRP feature display fish as arches. In this case, the arches will point upwards on the display screen. The fish are usually in motion as they move through the cone and cast back upwards a different signal depending on where the signal hits them.

The fish display on the screen as dots on fish finders with down imaging sonar. This is because it uses a narrower sonar cone, which means it only shows a part of the structure underneath the vessel. You can easily identify an individual fish and a school of fish with ease and precision once you get acclimatized. The user can identify fish arches and dots depending on the type of fish finder. You’ll be able to spot the lure once it hits the waters and the fish near it.

The size of the arches on the screen is directly proportional to the size of the fish. However, the size of the arches can also be as a result of the range setting. You can estimate the size of the fish basing on the size of the arch displayed on the screen with practice. Those who know how to read a fish finder can differentiate between signals that result from underwater structures and objects like rocks and plants and that of the fish.

Fish Icons

Most advanced fish finders have fish ID technology. This means that the fish finder model converts the sonar signals automatically to fish icons on the display screen. In this case, the user can identify the fish icons with ease. This idea sounds quite practical on paper but it’s not as easy in actual sense. This is because just like other technological features, it’s not 100% accurate meaning it can label underwater objects as fish. Plus, it can miss out on signals that are actual fish.

You’ll need to practice to get better at fish ID technology. This way, you’ll be able to tell the difference between underwater objects and fish on the display screen. However, most professional anglers usually prefer fish arches over fish icons because they think the latter is quite involving. With little practice and experience you’ll know how to read a fish finder correctly whether the screen is displaying fish arches, dots or icons.

How to Read Side Imaging vs Down Imaging Signals

Down imaging sonar uses a narrower sonar cone sent vertically into the water. This makes it ideal for viewing anything right under the boat in detail. Just as the name suggests, side imaging sonar uses two different sonar cones which are sent towards the right and left sideways. Side imaging helps the user get the general overview of the underwater topography on both sides of the boat.

It’s always advisable to use side imaging sonar to scout promising features once you hit the waters especially when it comes to the terrain. You can then switch to the down imaging sonar when look to identify fish in a particular location.

Estimating the Size of the Fish Displayed on the Fish Finder Screen

Generally, the size of the fish is directly proportional to the size of the dots or arches. However, you can glean more information from the fish arches basing on how wide and thick they are as well as their shape. Some fish finder models always show the width of the arches to help you estimate the length of the fish.

Save for the width, the shape of the arch is equally important. A bigger fish is usually displayed on the screen as a thick, full arch with clearly defined curves while their smaller counterparts show as narrow partial arches and slightly curved.

A school of small fish will show up as short lines or dots as opposed to arches. You can easily identify them as they tend to form a hanging cloud in the water. The behavior will also help you tell them apart from large fish species like bass that are solitary or form smaller groups with lots of space in between individuals.

The whole idea is to identify a school of fish in the water and other large predators underneath, which makes for the perfect place to cast the lure. You can drop the lure closer to them with little practice and experience especially when you focus on the fishing activity.

Reading Underwater Topography on the Screen of a Fish Finder

Apart from identifying fish on the display screen of a fish finder, you should also be conversant with the depth finder feature. The depth finder feature is either in meters or feet. The depth between the surface of the water and the bottom on most fish finder models is usually shown at the top corner on the left of the screen. The temperature of the water is right under the depth.

In addition, the fish finder’s display screen also gives a detailed information about bottom consistency and structure under the boat or kayak. You can identify any prominent structures like a sunken log or drop off that usually attracts a school of fish by moving across slowly. Use the wide beam setting to get a great overview of the underwater topography. With this, you can easily identify a promising fishing spot and the type of fish in that particular location.

Underwater weeds are displayed as narrow vertical lines on the fish finder’s display screen. Be on the lookout for depressions and holes since they tend to hold up lurking fish along with underwater mounds and logs that attract fish.

Bottom Consistency Types

You can learn about different types of bottom consistency with a little practice and experience depending on the sonar signal. A harder bottom typically shows up as a thicker and stronger line than a muddy bottom as it looks more fuzzy and broader on a fish finder model with 2D sonar.

Reading an Ice Fishing Flasher

A fishing flasher will come in handy for those who love ice fishing as they are specially designed for that purpose. A flasher fish finder displays only one dimensional readout from the water column under the ice hole unlike regular fish finders. However, you can also use a depth finder for ice fishing although positioning the transducer can be an uphill task. You can use a depth finder to shoot sonar right into the ice without necessarily drilling holes.

How to Read a Garmin Fish Finder Model

Garmin is a renowned brand that is known to make high-quality products and their fish finders are no exception. These fish finders are best suited for professional anglers and the novice alike since they are reliable. For instance, their echo series display the sonar cone at the right side of the display screen, corresponding with the water column right under the boat. Plus, it shows a live signal of anything detected at that particular time and location.


There’s a 2D sonar map on the left side showing what the sonar cone detected at that time. What’s more, the display screen has a color code that shows up in yellow to indicate a strong signal while red and blue means the signal is relatively weak. Fish are displayed as arches on the fish finder’s screen.

How to Read a Lowrance Fish Finder Model

Lowrance is equally popular in the fishing industry with lots of advantages. The best thing about Lowrance fish finder models is that they come with a HDI transducer that uses down imaging and 2D sonar simultaneously. This allows the user to select the split screen feature that shows sonar images on the left side of the display screen while the right side displays down imaging.

Both down imaging and 2D sonar have their own strengths and weaknesses. The latter gives you a detailed overview of the surrounding area. Down imaging, on the other part, gives information on fish and other underwater objects with a high resolution.

The sonar display on Lowrance fish finders is color coded with red and yellow indicating a strong signal. This means that the display will show a bright red and yellow when the receiver returns a strong signal while blue or grey is a clear indication of a weaker signal.


You’ll need a reliable source of power if you opt for a depth finder. I hope this article answers any questions you had about how to read a fish finder. Knowing how to read a fish finder and identifying the features on the screen correctly will give you a better fishing experience and also increase your chances of catching more fish.

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